Gather some old jeans, I used 3 because I wanted to reuse the pockets at the bottom of the legs and have 3 layers of denim in the front of the legs. One pair should fit over your regular riding wear so you can get them on easily. You also need a belt, 2 separating zippers, YKK are the best, 4 heavy duty snaps and knee pads. Got my knee pads from the thrift store.
Cut one pair in typical chap shape, retaining front pockets and waistband. Zig Zag raw edges or you can use bias tape or hem them. I liked the frayed look. Cut pockets you want from other pairs... I put them at the bottom of the legs for cell phone, camera, gloves, sunglasses etc. They are great when you are a passenger too!!
Split down outside of legs to accommodate zippers. I couldn't find zippers long enough for the whole leg, so I put two snaps at the bottom. You may have to do some trimming to get a snug fit around your upper thigh area. (A friend is useful at this step).
Depending on your sewing machine, you may need to attach the zippers to only 1 layer of denim. I am blessed with a heavy duty old Kenmore that will sew through leather and layers of denim like a hot knife through butter! haha
Cut the other jeans to fit where you want the most protection and attach to the inside or applique to the outside of your "chaps". (the backs of the jeans leg has the least wear to the fabric) This is also a good time to attach "pockets" to hold the knee pads so you can remove them before laundering. (another benefit of denim-wash-ability). You could also add rectangular patches of leather for added protection. Make sure you place them while your leg is bent so they aren't to high/low or too far on the inside/outside of your knee.
Attach pockets where they will be most useful but not distracting while you ride or walk around. *See photos
I threaded elastic through the waistband of the extra front pockets to secure items like my cell phone and camera. The larger pockets will even hold a standard bottle of water!
Cut 2 strips the full length of the side opening to make a flap to cover the zipper and snaps. Attach to the front section.
If cold is a factor, you could line with cotton flannel, fleece or fur. If heat is a factor, sacrificing an old mesh laundry bag would make a great air circulating liner. Nylon, rayon & polyester reduce friction between your clothes and the chaps but remember... synthetic fabrics have a lower melting temperature than natural ones (cotton/wool). Friction ---if you should happen to go down ---will cause the synthetic fabrics to melt into road rash and cause a very painful injury and prolonged recovery - this info from what I have read with regard to riding apparel and safety fabrics.
If you can afford it, you can purchase Kevlar or fire hose fabric from a specialty fabric supplier such as Alibaba.
Thanks for your interest! I wish you joyful riding!